EP1445761B1 - Apparatus and method for operating voice controlled systems in vehicles - Google Patents

Description

The invention relates to a method and a device for operating voice-assisted systems, such as communication and / or voice / intercom devices in motor vehicles, in which recorded via a microphone arrangement speech signals and transmitted to at least one speaker.

Methods of this type are used in motor vehicles for voice-assisted intercom operation or to support voice input controlled electronic or electrical assemblies. The fundamental problem here is that in the motor vehicle depending on the operating condition, a corresponding background noise is present. This covers the voice commands. Speech and intercom systems in motor vehicles are mainly advantageous for large vehicles, minibuses and the like. However, they can also be used in normal passenger cars. When using voice-controlled input units for electrical components in the vehicle, the suppression of the noise or the filtering of the voice command is still of particular importance.

So is out of the EP 0078014 B1 a speech recognition device for a motor vehicle, in which in the amplifier system of the speech recognition device is reported or fed via sensors, whether the engine is in operation and / or the vehicle is moving. Thereafter, a level control is aimed at trying to filter out the voice command from the background noise.

From the WO 97/34290 Filtering is known in which periodic interference signals are filtered out by determining their period and interpreting them by means of a generator so that the speech signal is left over.

From the DE 197 05 471 A1 It is known to support speech recognition using transversal filtering.

From the DE 41 06 405 C2 For example, a method is known in which a noise subtraction is performed from the speech signal using a plurality of microphones. An intercom with multiple microphones also discloses the DE 199 58 836 A1 ,

From the DE 39 25 589 A1 the use of a multiple microphone arrangement is known, wherein when used in the motor vehicle one of the microphones in the engine compartment and another is arranged in the passenger compartment. Then there is a subtraction of both signals. The disadvantage here is that only the engine noise or the actual operating noise of the vehicle itself is subtracted from the total signal in the passenger compartment. Specific noise is ignored. Likewise, a feedback suppression is missing. Wherever microphones and loudspeakers are arranged in acoustically coupled proximity, it happens that the acoustic signal coupled out at the loudspeaker feeds back into the microphone. It comes to a so-called feedback and a subsequent overload. Solutions for avoiding such overload are from the EP 1 077 013 B1 , of the WO 02/069487 A1 as well as the WO 02/21817 A2 known.

From the EP 0 903 726 A2 is an active noise and echo cancellation system is known, wherein from a microphone signal, a sine wave or a multiple sine wave is generated, by means of which the filter frequencies of a filter are adjusted set immediately.

From the WO 02/21817 A2 For example, a method and system for eliminating acoustic feedback is known wherein a current value taken by a microphone at a particular examination frequency is compared to a previously acquired value of the same examination frequency. The result of this comparison determines the parameters of a bandpass filter.

The invention is therefore the object of developing a method and a device of the generic type such that the verbal communication of the occupants of a vehicle is improved.

This object is achieved by a method according to claim 1 and a device according to claim 28. In this case, the operation of a voice-assisted system, such as a communication and / or voice / intercom in a motor vehicle, with at least one microphone and at least one speaker for reproducing a signal generated by the microphone and a arranged between the microphone and the speaker Bandpass- Filter the bandpass filter as a function of a comparison of the power of the signal generated by the microphone at an examination frequency with the power of the signal generated by the microphone at least a substantially integer multiples, ie a substantially harmonious, set the examination frequency. As examination frequency, one or more frequencies of the signal generated by means of the microphone come into question. In an advantageous embodiment of the invention, the frequency is selected as examination frequency at which the power of the signal generated by the microphone is substantially maximum. Alternatively, several frequency components with high powers are selected as examination frequencies.

In a further advantageous embodiment of the invention, the bandpass filter is both in response to a comparison of the power of the signal generated by the microphone at the examination frequency with the power of the signal generated by the microphone at least a substantially integer multiples of the examination frequency and in dependence Comparing the power of the signal generated by the microphone at the examination frequency with the power of the signal generated by the microphone at the examination frequency set at least one earlier time.

In a further advantageous embodiment of the invention, the bandpass filter is set such that it blocks the proportion of the signal generated by the microphone with a blocking frequency (only) if the power of the signal generated by the microphone at the examination frequency by more than an upper Limit is greater than the power of the signal generated by the microphone at the first harmonic of the examination frequency. Notch frequency in the sense of the invention may also be a frequency range and not just a single frequency.

In a further advantageous embodiment of the invention, the upper limit is between 20 and 40 dB. Distributively, the upper limit is substantially 30dB.

In a further advantageous embodiment of the invention, the bandpass filter is set so that it determines the proportion of the signal generated by the microphone with the Not inhibiting the blocking frequency if the power of the signal generated by the microphone at the examination frequency is greater than the power of the signal generated by the microphone at the first harmonic of the examination frequency by less than a lower limit.

In a further advantageous embodiment of the invention, the lower limit is between 5 and 20dB. Advantageously, the lower limit is substantially 12dB.

In a further advantageous embodiment of the invention is determined by comparing the power of the signal generated by the microphone at the examination frequency with the power of the signal generated by the microphone at the examination frequency at least earlier times, whether the power of the signal generated by the microphone in the Examination frequency increases exponentially.

In a further advantageous embodiment of the invention, the bandpass filter is set such that it blocks the proportion of the signal generated by the microphone at the blocking frequency when it is decided that the power of the signal generated by the microphone at the examination frequency increases exponentially.

In a further advantageous embodiment of the invention, the bandpass filter is set such that it blocks the proportion of the signal generated by the microphone with the blocking frequency (only) if the power of the signal generated by the microphone at the examination frequency longer than a first response time is greater than a threshold, the first response time advantageously being greater than substantially 750ms.

In a further advantageous embodiment of the invention, the power is determined at more than one examination frequency and the bandpass filter is set such that it blocks the proportion of the signal generated by the microphone with the blocking frequency only when the power of the signal generated by the microphone at a Examination frequency longer than a second response time is greater than the power of the signal generated by the microphone at any other examination frequency, the second response time is advantageously greater than substantially 750ms.

In a further advantageous embodiment of the invention, the setting of the bandpass filter is repeated with respect to the examination frequency earliest after a minimum dead time. The minimum dead time is advantageously 200ms to 300ms.

In a further advantageous embodiment of the invention, the bandpass filter is set so that it blocks the proportion of the signal generated by the microphone at a frequency range around the cutoff frequency, if after a repetition time, which is greater than the minimum dead time, the performance of is generated by the microphone at the examination frequency by more than the upper limit than the power of the signal generated by the microphone at the substantially first harmonic of the examination frequency and / or if it is decided that the power of the signal generated by the microphone at the examination frequency increases exponentially.

In a further advantageous embodiment of the invention, the bandpass filter is set so that it blocks the proportion of the signal generated by the microphone at an increased frequency range around the cutoff frequency, if after a repetition time, which is greater than the minimum dead time, the power the signal generated by the microphone at the examination frequency is greater than the upper limit of the power of the signal generated by the microphone at the substantially first harmonic of the examination frequency and / or if the power of the signal generated by the microphone is decided at the examination frequency increases exponentially.

Notch frequency For the purposes of the invention, the examination frequency may be at which the power of the signal generated by means of the microphone is maximum. In an advantageous embodiment of the invention, however, the rejection frequency is the examination frequency added at a correction frequency at which the power of the signal generated by the microphone is maximum, ie to the examination frequency at which the power of the signal generated by the microphone is maximum becomes a correction frequency added. This correction frequency is advantageously in

Dependence of the power of the signal generated by the microphone at the examination frequency at which the power of the signal generated by the microphone is maximum, and the power of the signal generated by the microphone at at least one, in particular directly, next to this examination frequency lying examination frequency formed.

gebildet werden, wobei

• fkorr die Korrekturfrequenz,
• fdist der Abstand zwischen der Untersuchungsfrequenz, bei der die Leistung des mittels des Mikrofons erzeugten Signals maximal ist, und einer die größte Leistung aufweisenden Untersuchungsfrequenz unmittelbar neben der Untersuchungsfrequenz, bei der die Leistung des mittels des Mikrofons erzeugten Signals maximal ist,
• Pmax die Leistung des mittels des Mikrofons erzeugten Signals bei der Untersuchungsfrequenz, bei der die Leistung des mittels des Mikrofons erzeugten Signals maximal ist (Pmax ist also die Leistung bei der Untersuchungsfrequenz, die größer ist als die Leistung jeder anderen Untersuchungsfrequenz),
• Pmaxneigh die Leistung des mittels des Mikrofons erzeugten Signals bei der die größte Leistung aufweisende
  Untersuchungsfrequenz unmittelbar neben der Untersuchungsfrequenz, bei der die Leistung des mittels des Mikrofons erzeugten Signals maximal ist, und
• sign ein Vorzeichen

ist, wobei sign positiv ist, wenn die die größte Leistung aufweisende Untersuchungsfrequenz unmittelbar neben der Untersuchungsfrequenz, bei der die Leistung des mittels des Mikrofons erzeugten Signals maximal ist, größer ist als die Untersuchungsfrequenz, bei der die Leistung des mittels des Mikrofons erzeugten Signals maximal ist, und wobei sign sonst negativ ist.Thus, the correction frequency, for example, according to $$\mathrm{Fcorr}=\mathrm{sign}*\mathrm{FDIST}*\mathrm{Pmaxneigh}/\left(\mathrm{Pmax}+\mathrm{Pmaxneigh}\right)$$

be formed, where

• fkorr the correction frequency,
• fd is the distance between the examination frequency at which the power of the signal generated by the microphone is maximum, and a test power having the highest performance immediately adjacent to the examination frequency at which the power of the signal generated by the microphone is maximum,
• Pmax the power of the signal generated by the microphone at the examination frequency at which the power of the signal generated by the microphone is maximum (Pmax is the power at the examination frequency which is greater than the power of any other examination frequency),
• Pmaxneigh the power of the signal generated by the microphone at the highest power
  Examination frequency immediately adjacent to the examination frequency at which the power of the signal generated by the microphone is maximum, and
• sign a sign

where sign is positive when the highest power examination frequency immediately adjacent to the examination frequency at which the power of the microphone generated signal is maximum is greater than the examination frequency at which the power of the microphone generated signal is maximum , and where else sign is negative.

• Es werden 192 Untersuchungsfrequenzen f₁, f₂, .... f₁₉₂ angenommen. f₁ ist gleich 40Hz. fdist ist für alle Untersuchungsfrequenzen 40Hz. Zudem gilt für die Leistungen des mittels des Mikrofons erzeugten Signals bei den Untersuchungsfrequenzen f₁, f₂, f_192: $$\mathrm{P}\left({\mathrm{f}}_{\mathrm{1}},{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="imgf0001.png,imgf0007.png"\; state="\{\{state\}\}">f</figure-callout>}}_{\mathrm{2}},\mathrm{....}{\mathrm{f}}_{\mathrm{94}}\right)=\mathrm{1}$$
  
  $$\mathrm{<figure-callout\; id="95"\; label="P\; f"\; filenames="imgf0010.png"\; state="\{\{state\}\}">P</figure-callout>}\left({\mathrm{f}}_{}\right)\left({\mathrm{}}_{\mathrm{95}}\right)=\mathrm{4}$$
  
  $$\mathrm{<figure-callout\; id="96"\; label="P\; f"\; filenames="imgf0010.png"\; state="\{\{state\}\}">P</figure-callout>}\left({\mathrm{f}}_{}\right)\left({\mathrm{}}_{96}\right)=16$$
  
  $$\mathrm{<figure-callout\; id="97"\; label="P\; f"\; filenames="imgf0010.png"\; state="\{\{state\}\}">P</figure-callout>}\left({\mathrm{f}}_{}\right)\left({\mathrm{}}_{97}\right)=2$$
  
  $$\mathrm{P}\left({\mathrm{f}}_{\mathrm{98}},{\mathrm{f}}_{\mathrm{99}},\mathrm{....}{\mathrm{f}}_{\mathrm{192}}\right)=\mathrm{1}$$
  

This is explained in more detail with reference to the following example:

• 192 examination frequencies f ₁ , f ₂ , .... f _{192 are} assumed. f ₁ is equal to 40Hz. fdist is 40Hz for all exam frequencies. In addition, for the powers of the signal generated by means of the microphone at the examination frequencies f ₁ , f ₂ , f _192: $$\mathrm{P}\left({\mathrm{f}}_{\mathrm{1}}.{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="imgf0001.png,imgf0007.png"\; state="\{\{state\}\}">f</figure-callout>}}_{\mathrm{2}}.\mathrm{....}{\mathrm{f}}_{\mathrm{94}}\right)=\mathrm{1}$$
  
  $$\mathrm{<figure-callout\; id="95"\; label="P\; f"\; filenames="imgf0010.png"\; state="\{\{state\}\}">P\; </figure-callout>}\left({\mathrm{f}}_{}\right)\left({\mathrm{}}_{\mathrm{95}}\right)=\mathrm{4}$$
  
  $$\mathrm{<figure-callout\; id="96"\; label="P\; f"\; filenames="imgf0010.png"\; state="\{\{state\}\}">P\; </figure-callout>}\left({\mathrm{f}}_{}\right)\left({\mathrm{}}_{96}\right)=16$$
  
  $$\mathrm{<figure-callout\; id="97"\; label="P\; f"\; filenames="imgf0010.png"\; state="\{\{state\}\}">P\; </figure-callout>}\left({\mathrm{f}}_{}\right)\left({\mathrm{}}_{97}\right)=2$$
  
  $$\mathrm{P}\left({\mathrm{f}}_{\mathrm{98}}.{\mathrm{f}}_{\mathrm{99}}.\mathrm{....}{\mathrm{f}}_{\mathrm{192}}\right)=\mathrm{1}$$
  

Then: $$\mathrm{Fcorr}=\left(-\right)*40\mathrm{Hz}*4/\left(16+2\right)=-\mathrm{8th}\mathrm{Hz}$$

The examination frequency at which the power of the signal generated by the microphone is maximum is thus 3840 Hz and the blocking frequency 3832 Hz.

zu bilden, wobei

• fkorr die Korrekturfrequenz,
• Δf der Abstand zwischen zwei Untersuchungsfrequenzen,
• Pmax die Leistung des mittels des Mikrofons erzeugten Signals bei der Untersuchungsfrequenz, bei der die Leistung des mittels des Mikrofons erzeugten Signals maximal ist,
• Pneighright die Leistung des mittels des Mikrofons erzeugten Signals bei der Untersuchungsfrequenz unmittelbar oberhalb (also rechts' neben) der Untersuchungsfrequenz, bei der die Leistung des mittels des Mikrofons erzeugten Signals maximal ist, und
• Pneighleft die Leistung des mittels des Mikrofons erzeugten Signals bei der Untersuchungsfrequenz unmittelbar unterhalb (also links' neben) der Untersuchungsfrequenz, bei der die Leistung des mittels des Mikrofons erzeugten Signals maximal ist,

ist.It has proven to be advantageous at least in certain embodiments, the correction frequency according to $$\mathrm{Fcorr}=\mathrm{.delta.f}*\left(\mathrm{Pneighright}-\mathrm{Pneighleft}\right)/\left(\mathrm{Pmax}+\left|\mathrm{Pneighright}-\mathrm{Pneighleft}\right|\right)$$

to form, being

• fkorr the correction frequency,
• Δf the distance between two examination frequencies,
• Pmax the power of the signal generated by the microphone at the examination frequency at which the power of the signal generated by means of the microphone is maximum,
• Pneighright the power of the signal generated by the microphone at the examination frequency immediately above (that is right 'next to) the examination frequency at which the power of the signal generated by the microphone is maximum, and
• Pneighleft the power of the signal generated by the microphone at the examination frequency immediately below (ie left 'next to) the examination frequency at which the power of the signal generated by the microphone is maximum,

is.

On the basis of the above numerical example, in this case: $$\mathrm{Fcorr}=40\mathrm{Hz}*\left(2-4\right)/\left(16+\left|4-2\right|\right)=-4.44\mathrm{Hz}$$

The examination frequency at which the power of the signal generated by the microphone is maximum is thus 3840 Hz and the blocking frequency 3835.56 Hz.

In a further advantageous embodiment of the invention, the distances between at least part of the examination frequencies or all examination frequencies are equidistant.

In a further advantageous embodiment of the invention, a presence of feedback is detected only if the power of the signal generated by the microphone at the examination frequency at which the power of the signal generated by the microphone is maximum by more than an upper limit is greater than the power of the signal generated by the microphone at the first harmonic of this examination frequency, wherein the upper limit is advantageously between 20 and 40 dB, in particular at substantially 30 dB.

In a further advantageous embodiment of the invention, the absence of feedback is determined when the power of the signal generated by the microphone at the examination frequency at which the power of the signal generated by the microphone is maximum by less than a lower limit is greater than the power of signal generated by the microphone at the first harmonic this examination frequency, wherein the lower limit is advantageously between 5 and 20 dB, in particular at substantially 12 dB.

In a further advantageous embodiment of the invention, a presence of feedback is (only) determined when the power of the signal generated by the microphone at the examination frequency at which the power of the signal generated by the microphone is maximum, at least approximately, increases exponentially.

In a further advantageous embodiment of the invention, a presence of feedback is (only) determined when the power of the signal generated by the microphone at at least one examination frequency is longer than a first response time greater than a threshold. The first response time is advantageously greater than substantially 750ms. The threshold can be selected depending on the power of the signal S or the sum of the power of all examination frequencies.

In a further advantageous embodiment of the invention, a presence of feedback (only) is determined if the power of the signal generated by the microphone at at least one examination frequency is longer than a first response time greater than the power of the signal generated by the microphone at any other examination frequency , The second response time is advantageously greater than substantially 750ms.

In a further advantageous embodiment of the invention, the adjustment of the bandpass filter is repeated at the earliest after a minimum dead time has expired, which is advantageously between 100 ms to 300 ms.

In a further advantageous embodiment of the invention, the power of the signal generated by means of the microphone is determined at at least 50, in particular at 150 to 300, examination frequencies.

In a further advantageous embodiment of the invention, the bandpass filter is a notch filter or a filter bank with at least one notch filter. The filter bank may include, for example, 10 notch filters.

Fig. 1

ein Kraftfahrzeug,

Fig. 2

ein Ausführungsbeispiel für eine erfindungsgemäße Einrichtung,

Fig. 3

ein Notchfilter,

Fig. 4

eine Filterbank,

Fig. 5

ein Ausführungsbeispiel für einen in einer Entscheidungslogik implementierten Ablaufpan,

Fig. 6

ein Leistung-Frequenz-Diagramm,

Fig. 7

ein Ausführungsbeispiel für Abfrage 41, in Fig. 5,

Fig. 8

ein Leistung-Frequenz-Diagramm,

Fig. 9

ein Leistung-Frequenz-Diagramm,

Fig. 10

ein weiteres Ausführungsbeispiel für Abfrage 41 in Fig. 5,

Fig. 11

ein weiteres Ausführungsbeispiel für einen in einer Entscheidungslogik implementierten Ablaufpan,

Fig. 12

ein Ausführungsbeispiel für die Abfragen 41 und 82,

Further advantages and details emerge from the following description of exemplary embodiments. Showing:

Fig. 1

a motor vehicle,

Fig. 2

an embodiment of an inventive device,

Fig. 3

a notch filter,

Fig. 4

a filter bank,

Fig. 5

an embodiment of a sequence implemented in a decision logic,

Fig. 6

a power-frequency diagram,

Fig. 7

an embodiment for query 41, in Fig. 5 .

Fig. 8

a power-frequency diagram,

Fig. 9

a power-frequency diagram,

Fig. 10

another embodiment for query 41 in Fig. 5 .

Fig. 11

a further embodiment of a sequence implemented in a decision logic,

Fig. 12

an embodiment for the queries 41 and 82,

Fig. 1 shows the interior view of a motor vehicle 1 from above. Here, reference numerals 2 and 3, the front seats and reference numerals 4, 5 and 6, the rear seats of the motor vehicle. Reference numerals 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 and 20 denote speakers. Reference numerals 21, 22, 23 and 24 denote microphones. The loudspeakers 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 and 20 are partly associated with a music system and partly with a communication / intercom device. They can also be used by both systems.

In the present exemplary embodiment, the loudspeakers 9, 17, 18, 19, 20 give a signal generated by the microphone 21, the loudspeakers 7, 17, 18, 19, 20 a signal generated by the microphone 22, the loudspeakers 7, 9, 19, 20 a signal generated by the microphone 23 and the speakers 7, 9, 17, 18 a signal generated by the microphone 24 from. In this way, the possibility of verbal communication in a motor vehicle is supported. In this case, the communication is in principle the better the stronger a signal between one of the microphones 21, 22, 23, 24 and one of the speakers 7, 9, 17, 18, 19, 20 is amplified. Limited is the possibility of one However, such gain due to possible feedback effects due to sound emitted by a loudspeaker 7, 9, 17, 18, 19, 20 received by a microphone 21, 22, 23, 24 and then amplified and through the speaker 7, 9, 17, 18, 19, 20 is broadcast.

To reduce such feedback is according to Fig. 2 between a microphone 30, which may be one of the microphones 21, 22, 23, 24, and a loudspeaker 31, which may be one of the loudspeakers 7, 9, 17, 18, 19, 20, a bandpass filter 32 is provided. This filters a signal S generated by the microphone 30 and provides a filtered signal S 'in which certain frequency ranges are filtered out, for which a decision logic 33 has recognized the risk of feedback. For this purpose, the decision logic 33 determines filter parameters f _c and Q by means of which the bandpass filter 32 is set.

To amplify the signal S and / or the signal S 'amplifiers, not shown, may be provided. However, the amplifier function can also be taken over by the bandpass filter.

Fig. 3 shows the characteristic of a designed as a notch filter bandpass filter, the gain V of the bandpass filter is plotted against the frequency f. Here f _c denotes the center frequency of the bandpass filter and Q its quality. For filtering a plurality of frequency ranges, the bandpass filter 32 is advantageously a filter bank, as in FIG Fig. 4 shown executed. The filter bank advantageously comprises up to 10 notch filters.

Fig. 5 shows an exemplary embodiment of an implemented in a decision logic 33 Ablaufpan. In this case, an examination frequency is first determined in a step 40. For this, the frequency f of the signal S is analyzed and, as exemplified in FIG Fig. 6 shown, the power P of the signal S an, for example 192, different examination frequencies f _n , f _{n + 1} , f _{n + 2} , f _{n + 3} , f _{n + 4} , f _{n + 5} , f _{n + 6} , f _{n +7} , f _{n + 8} determined, which are eg 40Hz apart. For the examination frequency f _{n + 5} , at which the power is maximum, the subsequent sequence is run through. However, it is also possible to go through the following procedure for more than one examination frequency.

It has proved to be advantageous to determine the power at the examination frequencies _fn , fn _{+ 1} , fn _{+ 2} , fn _{+ 3} , fn _{+ 4} , fn _{+ 5} , fn _{+ 6} , fn _{+ 7} , f _{n + 8} , ie to form an average value over time, and this time average of the power instead of the actual power of the signal S at the examination frequencies f _n , f _{n + 1} , f _{n + 2} , f _{n + 3} to investigate f _{n + 4} , f _{n + 5} , f _{n + 6} , f _{n + 7} , f _{n + 8} . If the power of the signal S is mentioned in the description and the claims, this can thus also include the average value of the power formed over a certain period of time. Furthermore, the term of the power according to the invention may include the amplitude or its time average. Also included in the sense of the invention are other modifications of the power, the amplitude or their time averages, such as normalized quantities. For example, under the power of the signal S at an examination frequency f _n in the sense of the invention, the value of the power of the signal S at this examination frequency f _{n can be} divided by the sum of the power of the signal S at all examination frequencies f _n , f _{n + 1} , f _{n + 2} , f _{n + 3} , f _{n + 4} , f _{n + 5} , f _{n + 6} , f _{n + 7} , f _{n + 8} .

The step 40 is followed by a query 41, if there is a risk of feedback. Details of this query are with respect to Fig. 7 and 10 executed. If there is a risk of feedback, query 41 is followed by a query 42 as to whether the signal S generated by the microphone 30 has already been reduced by signal components around the examination frequency by means of the bandpass filter.

If the signal S generated by the microphone 30 is not already reduced by signal components around the examination frequency by means of the bandpass filter, the query 42 is followed by a step 43 in which the filter parameters, ie the center frequency f _c and the quality Q of the bandpass filter Filters are generated. The center frequency f _c is an example of the blocking frequency in the sense of the claims. However, the blocking frequency in the sense of the claims can also be, in particular, the frequency range around the center frequency f _c , which the bandpass filter actually filters out of the signal S generated by the microphone 30.

gebildet werden, wobei

• fkorr die Korrekturfrequenz,
• fdist der Abstand zwischen der Untersuchungsfrequenz, bei der die Leistung des mittels des Mikrofons erzeugten Signals maximal ist, und einer die größte Leistung aufweisenden Untersuchungsfrequenz unmittelbar neben der Untersuchungsfrequenz, bei der die Leistung des mittels des Mikrofons erzeugten Signals maximal ist,
• Pmax die Leistung des mittels des Mikrofons erzeugten Signals bei der Untersuchungsfrequenz, bei der die Leistung des mittels des Mikrofons erzeugten Signals maximal ist,
• Pmaxneigh die Leistung des mittels des Mikrofons erzeugten Signals bei der die größte Leistung aufweisenden Unter-suchungsfrequenz unmittelbar neben der Untersuchungsfrequenz, bei der die Leistung des mittels des Mikrofons erzeugten Signals maximal ist, und
• sign ein Vorzeichen

ist, wobei sign positiv ist, wenn die die größte Leistung aufweisende Untersuchungsfrequenz unmittelbar neben der Untersuchungsfrequenz, bei der die Leistung des mittels des Mikrofons erzeugten Signals maximal ist, größer ist als die Untersuchungsfrequenz, bei der die Leistung des mittels des Mikrofons erzeugten Signals maximal ist, und wobei sign sonst negativ ist.The center frequency f _c can be set, for example, equal to the examination frequency. In an advantageous embodiment of the invention, however, the center frequency f _c is the examination frequency added at a correction frequency at which the power of the signal generated by the microphone is maximum, ie at the examination frequency at which the power of the signal generated by the microphone is maximum a Correction frequency added. This correction frequency is advantageously formed as a function of the power of the signal generated by the microphone at the examination frequency at which the power of the signal generated by the microphone is maximum, and the power of the signal generated by the microphone at at least one adjacent to this examination frequency examination frequency. Thus, the correction frequency, for example, according to $$\mathrm{Fcorr}=\mathrm{sign}*\mathrm{FDIST}*\mathrm{Pmaxneigh}/\left(\mathrm{Pmax}+\mathrm{Pmaxneigh}\right)$$

be formed, where

• fkorr the correction frequency,
• fd is the distance between the examination frequency at which the power of the signal generated by the microphone is maximum, and a test power having the highest performance immediately adjacent to the examination frequency at which the power of the signal generated by the microphone is maximum,
• Pmax the power of the signal generated by the microphone at the examination frequency at which the power of the signal generated by means of the microphone is maximum,
• Pmaxneigh the power of the signal generated by the microphone at the highest performance examination frequency immediately adjacent to the examination frequency at which the power of the signal generated by the microphone is maximum, and
• sign a sign

where sign is positive when the highest power examination frequency immediately adjacent to the examination frequency at which the power of the microphone generated signal is maximum is greater than the examination frequency at which the power of the microphone generated signal is maximum , and where else sign is negative.

gebildet, wobei

• fkorr die Korrekturfrequenz,
• Δf der Abstand zwischen zwei Untersuchungsfrequenzen,
• Pmax die Leistung des mittels des Mikrofons erzeugten Signals bei der Untersuchungsfrequenz, bei der die Leistung des mittels des Mikrofons erzeugten Signals maximal ist,
• Pneighright die Leistung des mittels des Mikrofons erzeugten Signals bei der Untersuchungsfrequenz unmittelbar oberhalb der Untersuchungsfrequenz, bei der die Leistung des mittels des Mikrofons erzeugten Signals maximal ist, und
• Pneighleft die Leistung des mittels des Mikrofons erzeugten Signals bei der Untersuchungsfrequenz unmittelbar unterhalb der Untersuchungsfrequenz, bei der die Leistung des mittels des Mikrofons erzeugten Signals maximal ist,

ist.In the present embodiment, the correction frequency according to $$\mathrm{Fcorr}=\mathrm{.delta.f}*\left(\mathrm{Pneighright}-\mathrm{Pneighleft}\right)/\left(\mathrm{Pmax}+\left|\mathrm{Pneighright}-\mathrm{Pneighleft}\right|\right)$$

formed, where

• fkorr the correction frequency,
• Δf the distance between two examination frequencies,
• Pmax the power of the signal generated by the microphone at the examination frequency at which the power of the signal generated by means of the microphone is maximum,
• Pneighright the power of the signal generated by the microphone at the examination frequency immediately above the examination frequency at which the power of the signal generated by the microphone is maximum, and
• Pneighleft the power of the signal generated by the microphone at the examination frequency immediately below the examination frequency at which the power of the signal generated by the microphone is maximum,

is.

The quality Q is set to a predetermined value of e.g. 1 / 40Hz set.

Step 43 is followed by inquiry 45 as to whether the program should be terminated. If the program is not terminated, the query 45 follows step 40. Otherwise, the program is terminated.

If the signal S generated by the microphone 30 is already reduced by signal components around the examination frequency by means of the bandpass filter, the query 43 is followed by a step 44, in which the quality Q is reduced. Thereby, the bandpass filter is adjusted so that it blocks the proportion of the signal generated by the microphone at an increased frequency range around the center frequency f _c around. Step 44 is followed by step 40.

If there is no risk of feedback, query 41 is followed by query 45, or optionally a step 46, in which the filtering of the signal S generated by the microphone 30 is terminated by the examination frequency.

In a particularly advantageous embodiment, it is provided that the query 41 is repeated at the earliest after the expiration of a minimum dead time, wherein the minimum dead time in the present embodiment is 200 ms to 300 ms.

Fig. 7 shows an embodiment of the query 41. In this case, first a query 50 is provided, whether the power of the signal generated by the microphone 30 S at the examination frequency by not less than a lower limit is greater than the power of the signal generated by the microphone 30 S. at the first harmonic (ie twice) of the examination frequency. The lower limit Δ1 is for example between 5 and 20 dB. Advantageously, the lower limit Δ1 is substantially 12dB. This query illustrates by way of example Fig. 8 , where f _H0 denotes the examination _frequency , f _H1 , f _H2 , f _H3 and f _H4 the first, second, third and fourth harmonics of the examination _frequency and f _H½ the first subharmonic of the examination _frequency . P denotes the power at a frequency f. With query 50 is thus queried whether $$\mathrm{P}\left({\mathrm{f}}_{\mathrm{H}\mathrm{0}}\right)-\mathrm{<figure-callout\; id="1"\; label="P\; f\; H"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">P\; </figure-callout>}\left({\mathrm{f}}_{\mathrm{H}}\right)\left({\mathrm{}\mathrm{1}}_{}\right)\ge \mathrm{<figure-callout\; id="1"\; label="\Delta "\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">\Delta </figure-callout>}\mathrm{1}$$

$$\mathrm{P}\left({\mathrm{f}}_{\mathrm{H}\mathrm{0}}\right)-\mathrm{P}\left({\mathrm{f}}_{\mathrm{H}\mathrm{2}}\right)\ge \mathrm{\Delta }\mathrm{1}$$

$$\mathrm{P}\left({\mathrm{f}}_{\mathrm{H}\mathrm{0}}\right)-\mathrm{P}\left({\mathrm{f}}_{\mathrm{H}\mathrm{3}}\right)\ge \mathrm{\Delta }\mathrm{1}$$

$$\mathrm{P}\left({\mathrm{f}}_{\mathrm{H}\mathrm{0}}\right)-\mathrm{P}\left({\mathrm{f}}_{\mathrm{H}\mathrm{4}}\right)\ge \mathrm{\Delta }\mathrm{1}$$

zu ergänzen, wobei gegebenenfalls auch andere Grenzwerte gewählt werden können.Optionally, query 50 may be provided for one or more of the queries $$\mathrm{P}\left({\mathrm{f}}_{\mathrm{H}\mathrm{0}}\right)-\mathrm{<figure-callout\; id="1"\; label="P\; f\; H"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">P\; </figure-callout>}\left({\mathrm{f}}_{\mathrm{H}}\right)\left({\mathrm{}\mathrm{1}/\mathrm{2}}_{}\right)\ge \mathrm{\Delta }\mathrm{1}$$

$$\mathrm{P}\left({\mathrm{f}}_{\mathrm{H}\mathrm{0}}\right)-\mathrm{<figure-callout\; id="2"\; label="P\; f\; H"\; filenames="imgf0001.png,imgf0007.png"\; state="\{\{state\}\}">P\; </figure-callout>}\left({\mathrm{f}}_{\mathrm{H}}\right)\left({\mathrm{}\mathrm{2}}_{}\right)\ge \mathrm{\Delta }\mathrm{1}$$

$$\mathrm{P}\left({\mathrm{f}}_{\mathrm{H}\mathrm{0}}\right)-\mathrm{<figure-callout\; id="3"\; label="P\; f\; H"\; filenames="imgf0001.png"\; state="\{\{state\}\}">P\; </figure-callout>}\left({\mathrm{f}}_{\mathrm{H}}\right)\left({\mathrm{}\mathrm{3}}_{}\right)\ge \mathrm{\Delta }\mathrm{1}$$

$$\mathrm{P}\left({\mathrm{f}}_{\mathrm{H}\mathrm{0}}\right)-\mathrm{P}\left({\mathrm{f}}_{\mathrm{H}\mathrm{4}}\right)\ge \mathrm{<figure-callout\; id="1"\; label="\Delta "\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">\Delta </figure-callout>}\mathrm{1}$$

to supplement, where appropriate, other limits can be selected.

The examination frequencies f _n , f _{n + 1} , f _{n + 2} , f _{n + 3} , f _{n + 4} , f _{n + 5} , f _{n + 6} , f _{n + 7} , f _{n + 8} in Fig. 6 are of the subharmonic / harmonics f _H½ , f _H1 , f _H2 , f _H3 and f _H4 in Fig. 8 respectively. Fig. 9 to distinguish. For example, assume 192 examination frequencies f _1, f ₂ , .... f ₁₉₂ , which are 40Hz apart, where f ₁ is 40Hz, and f ₄₄ = f _H0 , ie the examination frequency at which the power of the microphone 30th is maximum, so f _H1 = f ₈₈ and f _H2 = f ₁₂₂ .

If the power of the signal S generated by means of the microphone 30 at the examination frequency is not less than a lower limit Δ1 greater than the power of the signal S generated by the microphone 30 at the first harmonic of the examination frequency, the query 50 is followed by a query 51. The query 51 queries whether the power of the signal S generated by means of the microphone 30 at the examination frequency is greater than the power of the microphone 30 generated by not less than an upper limit Δ 2 Signal S at the first harmonic of the examination frequency. The upper limit Δ2 is for example between 20 and 40 dB. Advantageously, the upper limit Δ2 is substantially 30 dB. This query illustrates by way of example Fig. 9 where again f _H0 denotes the examination _frequency , f _H1 , f _H2 , f _H3 and f _H4 the first, second, third and fourth harmonics of the examination _frequency and f _H½ the first subharmonic of the examination _frequency . P again denotes the power at a frequency f. With query 51 is thus queried whether $$\mathrm{P}\left({\mathrm{f}}_{\mathrm{H}\mathrm{0}}\right)-\mathrm{<figure-callout\; id="1"\; label="P\; f\; H"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">P\; </figure-callout>}\left({\mathrm{f}}_{\mathrm{H}}\right)\left({\mathrm{}\mathrm{1}}_{}\right)\ge \mathrm{<figure-callout\; id="2"\; label="\Delta "\; filenames="imgf0001.png,imgf0007.png"\; state="\{\{state\}\}">\Delta </figure-callout>}\mathrm{2}$$

$$\mathrm{P}\left({\mathrm{f}}_{\mathrm{H}\mathrm{0}}\right)-\mathrm{P}\left({\mathrm{f}}_{\mathrm{H}\mathrm{2}}\right)\ge \mathrm{\Delta }\mathrm{2}$$

$$\mathrm{P}\left({\mathrm{f}}_{\mathrm{H}\mathrm{0}}\right)-\mathrm{P}\left({\mathrm{f}}_{\mathrm{H}\mathrm{3}}\right)\ge \mathrm{\Delta }\mathrm{2}$$

$$\mathrm{P}\left({\mathrm{f}}_{\mathrm{H}\mathrm{0}}\right)-\mathrm{P}\left({\mathrm{f}}_{\mathrm{H}4}\right)\ge \mathrm{\Delta }\mathrm{2}$$

zu ergänzen, wobei gegebenenfalls auch andere Grenzwerte gewählt werden können.Optionally, query 51 may be provided for one or more of the queries $$\mathrm{P}\left({\mathrm{f}}_{\mathrm{H}0}\right)-\mathrm{<figure-callout\; id="1"\; label="P\; f\; H"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">P\; </figure-callout>}\left({\mathrm{f}}_{\mathrm{H}}\right)\left({\mathrm{}1/2}_{}\right)\ge \mathrm{\Delta }2$$

$$\mathrm{P}\left({\mathrm{f}}_{\mathrm{H}\mathrm{0}}\right)-\mathrm{<figure-callout\; id="2"\; label="P\; f\; H"\; filenames="imgf0001.png,imgf0007.png"\; state="\{\{state\}\}">P\; </figure-callout>}\left({\mathrm{f}}_{\mathrm{H}}\right)\left({\mathrm{}\mathrm{2}}_{}\right)\ge \mathrm{\Delta }\mathrm{2}$$

$$\mathrm{P}\left({\mathrm{f}}_{\mathrm{H}\mathrm{0}}\right)-\mathrm{<figure-callout\; id="3"\; label="P\; f\; H"\; filenames="imgf0001.png"\; state="\{\{state\}\}">P\; </figure-callout>}\left({\mathrm{f}}_{\mathrm{H}}\right)\left({\mathrm{}\mathrm{3}}_{}\right)\ge \mathrm{\Delta }\mathrm{2}$$

$$\mathrm{P}\left({\mathrm{f}}_{\mathrm{H}\mathrm{0}}\right)-\mathrm{P}\left({\mathrm{f}}_{\mathrm{H}4}\right)\ge \mathrm{<figure-callout\; id="2"\; label="\Delta "\; filenames="imgf0001.png,imgf0007.png"\; state="\{\{state\}\}">\Delta </figure-callout>}\mathrm{2}$$

to supplement, where appropriate, other limits can be selected.

If the power of the signal S generated by means of the microphone 30 at the examination frequency is not greater than the power of the signal S generated by the microphone 30 at the first harmonic of the examination frequency by more than an upper limit Δ2, the query 51 is followed by a query 52, by means of the signal S produced at the examination frequency by comparing the power of the signal S generated by means of the microphone 30 with the power of the signal S generated by the microphone 30 at the examination frequency at least at an earlier point in time, whether the power of the signal generated by means of the microphone is determined by the Examination frequency increases exponentially.

Fig. 10 shows a further embodiment of the query 41. Here, a query 60 is first provided, whether the power of the signal generated by the microphone 30 S at the examination frequency is greater than a predetermined limit. In this case, a query 61 follows, which corresponds to the query 50. The queries 62 and 63 correspond to the queries 51 and 52.

Fig. 11 shows a preferred embodiment for a process implemented in the decision logic 33 Ablaufpan. The process starts with a step 81, which is the step 40 in Fig. 5 equivalent. Step 81 is followed by a query 41 in FIG Fig. 5 corresponding query 82, if there is a risk of feedback. Embodiments for the query 82 show Fig. 7 and Fig. 10 , In connection with the embodiment in Fig. 11 has an implementation of a feedback detection (query 82), as in Fig. 12 is explained in more detail, found to be advantageous.

Unless the risk of feedback exists or is found, the query 82 follows a query 45 corresponding query 83, whether the program should be terminated. If the program is not terminated, the query 93 follows the step 81. Otherwise, the program is terminated.

If there is a risk of feedback, the query 82 is followed by a query 83 corresponding to the query 42 as to whether the signal S generated by the microphone 30 has already been reduced by signal components around the examination frequency by means of the bandpass filter. If the signal S generated by the microphone 30 is already reduced by signal components around the examination frequency by means of the bandpass filter, the query 83 is followed by a query 85, otherwise a query 84.

Query 84 queries whether a notch filter is available. If a notch filter is available, query 84 is followed by a step 88 corresponding to step 43, in which the filter parameters, ie the center frequency f _c and the quality Q of the bandpass filter for the specific embodiment, are generated. If query 84 indicates that no notch filter is available, query 84 is followed by a step 86 in which the power of signal S is reduced by a reduction factor which is advantageously between 2 dB and 5 dB, in particular at substantially 3dB , Step 86 is followed by a step 87 in which the entire run is stopped for a stop time of substantially 3 seconds. However, this step should only be executed once per run.

By means of the query 85 it is queried whether a further expansion of the frequency range in which the bandpass filter blocks, that is to say by a further reduction of its quality Q, would fall below a predetermined minimum quality. If a predetermined minimum quality were undershot by a further widening of the frequency range, the query 85 is followed by a step 89, otherwise by a step 91. In step 91, which corresponds to step 44, the quality Q is reduced.

Steps 87, 88 and 91 are followed by a step 92, in which the process is stopped for a minimum dead time, the minimum dead time in the present embodiment being 100 ms.

In step 89, the power of the signal S is reduced by a reduction factor which is advantageously between 2dB and 5dB, in particular at substantially 3dB. Step 89 is followed by a step 90 in which the entire run is stopped for a stop time of substantially 3 seconds.

Fig. 7 shows an embodiment for the query 82, according to which also query 41 can be implemented. In this case, a query 95 is initially provided as to whether the power of the signal S generated by means of the microphone 30 at the examination frequency is greater than 750 ms greater than the power of the signal S produced by the microphone 30 of every other examination frequency. If the power of the signal S generated by means of the microphone 30 at the examination frequency is greater than 750 ms greater than the power of the signal S generated by the microphone 30 of every other examination frequency, the query 95 is followed by a query 96. Otherwise, the query 95 follows the query 93rd

The query 96 queries whether the power of the signal S generated by means of the microphone 30 at the examination frequency is not greater than 12 dB greater than the power of the signal S generated by the microphone 30 at the first harmonic (ie twice) of the examination frequency is. If the power of the signal S generated by means of the microphone 30 at the examination frequency is not greater than 12 dB greater than the power of the signal S generated by the microphone 30 at the first harmonic of the examination frequency, the query 96 is followed by a query 97. Otherwise, it follows the query 96 the query 93.

The query 97 queries whether the power of the signal S generated by the microphone 30 at the examination frequency is greater than 750 ms greater than a response threshold. If the power of the signal S generated by means of the microphone 30 at the examination frequency is greater than a response threshold for more than 750 ms, the query 97 follows the query 83. Otherwise, the query 95 is followed by the query 93.

The feedback detection according to the invention is not based on the embodiments Fig. 7 . Fig. 10 and Fig. 12 limited. It can be provided, for example, that the queries 52 and 63 follow the no outputs of the queries 50 and 61, respectively. In addition, it can be provided, the embodiments according to Fig. 7 . Fig. 10 and Fig. 12 with their binary decision logic by a fuzzy decision logic, so to replace fuzzy logic or neural networks. <B> LIST OF REFERENCES </ b> 1 motor vehicle 2, 3 front seats 4, 5, 6 rear seats 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 31 speaker 21, 22, 23, 24, 30 Microphones 32 Bandpass filter 33 decision logic 40, 41, 43, 44, 46, 81, 84, 86, 87, 88, 89, 90 91, 92 steps 41, 42, 45, 50, 51, 52, 60, 61, 62, 63, 82, 83, 84, 85, 93, 95, 96, 97 Interrogate f frequency f _H0 test frequency f _H1 first harmonic of the examination frequency f _H2 second harmonic of the examination frequency f _H3 third harmonic of the examination frequency f _H4 fourth harmonic of the examination frequency f _H½ first subharmonic of the examination frequency f _n , f _{n + 1} , f _{n + 2} , f _{n + 3} , f _{n + 4} , f _{n + 5} , f _{n + 6} , f _{n + 7} , f _{n + 8} , f ₁ ,. f ₂ ,. f _44,. f _88,. f _94,. f ₉₅ , f ₉₇ , .ff ₉₈ ,. f _122,. f ₁₉₂ frequency points f _c center frequency FDIST The distance between the examination frequency at which the power of the signal generated by the microphone is maximum and the highest performance examination frequency immediately adjacent to the examination frequency at which the power of the signal generated by the microphone is maximum Fcorr correction frequency Q quality P power Pmax Power of the signal generated by the microphone at the examination frequency at which the power of the signal generated by the microphone is maximum Pmaxneigh Power of the signal generated by the microphone at the highest power examination frequency immediately adjacent to the examination frequency at which the power of the signal generated by the microphone is maximum Pneighleft Power of the signal generated by the microphone at the examination frequency immediately below the examination frequency at which the power of the signal generated by the microphone is maximum Pneighright Power of the signal generated by the microphone at the examination frequency immediately above the examination frequency at which the power of the signal generated by the microphone is maximum S signal S ' filtered signal sign sign V reinforcement Δ1 lower limit Δ2 upper limit .delta.f Distance between two examination frequencies

Claims (29)

1. Method for operating a voice-assisted system, such as a communication and/or voice/intercom device in a motor vehicle (1), having at least one microphone (30) and at least one loudspeaker (31) for reproducing a signal (S) generated using the microphone (30) and having a bandpass filter (32) arranged between the microphone (30) and the loudspeaker (31),
   characterized in that
   the bandpass filter (32) is set on the basis of a comparison of the power of the signal (S) generated using the microphone (30) at an investigation frequency (fn+5), at which the power of the signal generated using the microphone is substantially at a maximum, with the power of the signal (S) generated using the microphone (30) at at least a substantially integer multiple of the investigation frequency (fn+5).
2. Method according to Claim 1, characterized in that the bandpass filter (32) is set on the basis of a comparison of the power of the signal (S) generated using the microphone (30) at the investigation frequency (fn+5) with the power of the signal (S) generated using the microphone (30) at the investigation frequency (fn+5) at at least one earlier time.
3. Method according to Claim 1 or 2, characterized in that the bandpass filter (32) is set in such a manner that it blocks the proportion of the signal (S) generated using the microphone (30) at a blocking frequency if the power of the signal (S) generated using the microphone (30) at the investigation frequency (f_n+5) is greater than the power of the signal (S) generated using the microphone (30) at the first harmonic of the investigation frequency (f_n+5) by more than an upper limit value (Δ2).
4. Method according to Claim 3, characterized in that the upper limit value (Δ2) is between 20 and 40 dB.
5. Method according to Claim 4, characterized in that the upper limit value (Δ2) is substantially 30 dB.
6. Method according to one of the preceding claims, characterized in that the bandpass filter (32) is set in such a manner that it does not block the proportion of the signal (S) generated using the microphone (30) at the blocking frequency if the power of the signal (S) generated using the microphone (30) at the investigation frequency (f_n+5) is greater than the power of the signal (S) generated using the microphone (30) at the first harmonic of the investigation frequency (f_n+5) by less than a lower limit value (Δ1).
7. Method according to Claim 6, characterized in that the lower limit value (Δ1) is between 5 and 20 dB.
8. Method according to Claim 7, characterized in that the lower limit value (Δ1) is substantially 12 dB.
9. Method according to one of the preceding claims, characterized in that a comparison of the power of the signal (S) generated using the microphone (30) at the investigation frequency (f_n+5) with the power of the signal (S) generated using the microphone (30) at the investigation frequency (f_n+5) at at least earlier times is used to decide whether the power of the signal (S) generated using the microphone (30) at the investigation frequency (f_n+5) rises exponentially.
10. Method according to Claim 9, characterized in that the bandpass filter (32) is set in such a manner that it blocks the proportion of the signal (S) generated using the microphone (30) at the blocking frequency if it is decided that the power of the signal (S) generated using the microphone (30) at the investigation frequency (f_n+5) rises exponentially.
11. Method according to one of the preceding claims, characterized in that the bandpass filter (32) is set in such a manner that it blocks the proportion of the signal (S) generated using the microphone (30) at the blocking frequency only if the power of the signal (S) generated using the microphone (30) at the investigation frequency (f_n+5) is greater than a response threshold for longer than a first response time.
12. Method according to Claim 11, characterized in that the first response time is greater than substantially 750 ms.
13. Method according to one of the preceding claims, characterized in that the power is determined at more than one investigation frequency (f_n, f_n+1, f_n+2, f_n+3, f_n+4, f_n+5, f_n+6, f_n+₇, f_n+8), and in that the bandpass filter (32) is set in such a manner that it blocks the proportion of the signal (S) generated using the microphone (30) at the blocking frequency only if the power of the signal (S) generated using the microphone (30) at an investigation frequency (f_n+5) is greater than the power of the signal (S) generated using the microphone (30) at every other investigation frequency (f_n, f_n+1, f_n+2, f_n+3, f_n+4, f_n+6, f_n+7, f_n+8) for a longer than a second response time.
14. Method according to Claim 13, characterized in that the second response time is greater than substantially 750 ms.
15. Method according to one of the preceding claims, characterized in that the setting of the bandpass filter (32) with respect to the investigation frequency (f_n+5) is repeated at the earliest after expiry of a minimum dead time.
16. Method according to Claim 15, characterized in that the minimum dead time is 100 ms to 300 ms.
17. Method according to Claim 15 or 16, characterized in that the bandpass filter (32) is set in such a manner that it blocks the proportion of the signal (S) generated using the microphone (30) in a frequency range around the blocking frequency if, after expiry of a repetition time which is greater than the minimum dead time, the power of the signal (S) generated using the microphone (30) at the investigation frequency (f_n+5) is greater than the power of the signal (S) generated using the microphone (30) at the first harmonic of the investigation frequency (f_n+5) by more than the upper limit value (Δ2) and/or if it is decided that the power of the signal (S) generated using the microphone (30) at the investigation frequency (f_n+5) rises exponentially.
18. Method according to Claim 15, 16 or 17, characterized in that the bandpass filter (32) is set in such a manner that it blocks the proportion of the signal (S) generated using the microphone (30) in an increased frequency range around the blocking frequency if, after expiry of a repetition time which is greater than the minimum dead time, the power of the signal (S) generated using the microphone (30) at the investigation frequency (f_n+5) is greater than the power of the signal (S) generated using the microphone (30) at the first harmonic of the investigation frequency (f_n+5) by more than the upper limit value (Δ2) and/or if it is decided that the power of the signal (S) generated using the microphone (30) at the investigation frequency (f_n+5) rises exponentially.
19. Method according to Claim 18, characterized in that the frequency range around the blocking frequency is increased only to a minimum quality.
20. Method according to Claim 19, characterized in that the signal (S) generated using the microphone (30) is interrupted for an interruption period if the frequency range around the blocking frequency is increased to the minimum quality.
21. Method according to Claim 20, characterized in that the interruption period is greater than substantially 1 s to 5 s.
22. Method according to Claim 21, characterized in that the interruption period is greater than substantially 3 s.
23. Method according to one of Claims 3 to 22, characterized in that the blocking frequency is the investigation frequency (f_n+5) at which the power of the signal (S) generated using the microphone (30) is at a maximum.
24. Method according to one of Claims 3 to 22, characterized in that the blocking frequency is the investigation frequency (f_n+5) at which the power of the signal (S) generated using the microphone (30) is at a maximum and to which a correction frequency has been added.
25. Method according to Claim 24, characterized in that the correction frequency is formed on the basis of the power of the signal (S) generated using the microphone (30) at the investigation frequency (f_n+5), at which the power of the signal (S) generated using the microphone (30) is at a maximum, and the power of the signal (S) generated using the microphone (30) at at least one investigation frequency (f_n+4) beside this investigation frequency (f_n+5).
26. Method according to Claim 25, characterized in that the correction frequency is formed according to $$\mathrm{fkorr}=\mathrm{sign}*\mathrm{fdist}*\mathrm{Pmaxneigh}/\left(\mathrm{Pmax}+\mathrm{Pmaxneigh}\right),\mathrm{where}$$

    

    where

    - fkorr is the correction frequency,

    - fdist is the distance between the investigation frequency (f_n+5), at which the power of the signal (S) generated using the microphone (30) is at a maximum, and an investigation frequency (f_n+4) having the greatest power directly beside the investigation frequency (f_n+5) at which the power of the signal (S) generated using the microphone (30) is at a maximum,

    - Pmax is the power of the signal (S) generated using the microphone (30) at the investigation frequency (f_n+5) at which the power of the signal (S) generated using the microphone (30) is at a maximum,

    - Pmaxneigh is the power of the signal (S) generated using the microphone (30) at the investigation frequency (f_n+4) having the greatest power directly beside the investigation frequency (f_n+5) at which the power of the signal (S) generated using the microphone (30) is at a maximum, and

    - sign is a mathematical sign,

    where sign is positive if the investigation frequency (f_n+4) having the greatest power directly beside the investigation frequency (f_n+5), at which the power of the signal (S) generated using the microphone (30) is at a maximum, is greater than the investigation frequency (f_n+5) at which the power of the signal (S) generated using the microphone (30) is at a maximum, and where sign is otherwise negative.
27. Method according to Claim 25, characterized in that the correction frequency is formed according to $$\mathrm{fkorr}=\mathrm{\Delta f}*\left(\mathrm{Pneighright}-\mathrm{Pneighleft}\right)/\left(\mathrm{Pmax}+\left|\mathrm{Pneighright}-\mathrm{Pneighleft}\right|\right),$$

    

    where

    - fkorr is the correction frequency,

    - Δf is the distance between two investigation frequencies (f_n, f_n+1, f_n+2, f_n+3, t_n+4, f_n+5, f_n+6, f_n+7, f_n+8),

    - Pmax is the power of the signal (S) generated using the microphone (30) at the investigation frequency (f_n+5) at which the power of the signal (S) generated using the microphone (30) is at a maximum,

    - Pneighright is the power of the signal (S) generated using the microphone (30) at the investigation frequency (f_n+6) directly above the investigation frequency (f_n+5) at which the power of the signal (S) generated using the microphone (30) is at a maximum, and

    - Pneighleft is the power of the signal (S) generated using the microphone (30) at the investigation frequency (f_n+4) directly below the investigation frequency (f_n+5) at which the power of the signal (S) generated using the microphone (30) is at a maximum.
28. Device for operating voice-assisted systems in accordance with a method according to one of the preceding claims, the device having at least one microphone (30) and at least one loudspeaker (31) for reproducing a signal (S) generated using the microphone (30) and a bandpass filter (32) arranged between the microphone (30) and the loudspeaker, and the device having decision logic for setting the bandpass filter (32) on the basis of a comparison of the power of the signal (S) generated using the microphone (30) at an investigation frequency (f_n+5), at which the power of the signal generated using the microphone is substantially at a maximum, with the power of the signal (S) generated using the microphone (30) at at least a substantially integer multiple of the investigation frequency (fn+5).
29. Device according to Claim 28, characterized in that the bandpass filter (32) is a filter bank having at least one notch filter.

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